It is well known in the preparation of epoxide resins, which are generally glycidyl polyethers of polyhydric alcohols, that they can be cured by reacting with a polyamine. There is substantial literature available with respect to various types of amine curing agents for polyepoxide resin systems and representative literature include the following patents:
U.S. Pat. No. 2,817,644 discloses reacting polyepoxide resins with hydrogenated aromatic primary or secondary diamines where the aromatic amine has at least two amine hydrogens. Aromatic polyamines which are suited for hydrogenation include phenylenediamine, toluenediamine, 3,3'-diaminodiphenyl, p,p'-methylenedianiline and so forth. The hydrogenated aromatic amines provide epoxy resin products having excellent hardness and excellent resistance to solvents and water.
U.S. Pat. Nos. 3,427,282 and 3,560,443 disclose the curing of epoxy resins with 4,4'-methylene-bis(2-alkylanilines) such as 4,4'-methylene-bis(2-ethylaniline) and 4,4'-methylene-bis(2-isopropylaniline). Utilization of these aromatic amine curing agents provide for extended pot life in epoxy resins relative to methylenedi(aniline). The '443 patent discloses a variation to the '282 disclosure in that epoxy resins are cured with the 4,4'-methylene-bis(2-alkyl-6-methylaniline) derivatives. In contrast to the '282 patent the amine in the '443 patent is a dialkyl substituted bridged aromatic amine having alkyl groups in each ortho position to each amine group. The '443 curing agents provide for extended pot life and yet provide epoxy resins having a good heat distortion temperatures.
U.S. Pat. No. 3,351,610 discloses the use of di-tertiary alkylene-bis(cyclohexylamines) which include 2,2-bis(4-dimethylaminocyclohexyl)propane and bis(4-dimethylaminocyclohexyl)methane as curing catalysts. In contrast to prior art tertiary amines, they provide epoxy resins having good mechanical properties in terms of flexural strength, impact strength, etc. Prior to this development it was customary to use primary and secondary amines where the amines would react with the epoxy resin for crosslinking.
U.S. Pat. No. 3,629,181 discloses adducts of polyepoxide resins and cycloaliphatic or cycloaliphatic-aliphatic di-primary diamines. Cycloaliphatic di-primary amines suited for adduct formation include diaminocyclohexanes and bridged cyclohexylamines where the bridge is a methylene or a propylidene group and representative compounds include 2,2-di(4-aminocyclohexyl)propane and 4,4'-methylene-bis(2-methylcyclohexylamine). Also included is 3-aminomethyl-3,5,5-trimethyl-1-cyclohexylamine or isophoronediamine as it is sometimes called.
U.S. Pat. No. 4,525,571 discloses the formation of surface coatings comprising epoxy resins and amine curing agents such as a cycloaliphatic di-primary amines, e.g. 1,2-diaminocyclohexane.
U.S. Pat. No. 4,293,687 discloses various tetraalkylated bis(cyclohexylamine) derivatives which include bis(3,5-dimethyl-4-aminocyclohexyl)methane and bis(3,5-diethyl-4-aminocyclohexyl)methane. These bridged cyclohexylamine derivatives are suggested as being suited as valuable intermediate products for the production of polycondensation resins and lacquers. Representative condensation resins include polyurethanes and polyamides.
U.S. Pat. No. 4,946,925 discloses various bridged bi(cyclohexylamine) derivatives as curing agents. Each cyclohexylamine group has two alkyl groups where the alkyl groups are in the 2 and the 5 position and the main groups are in the 4 position. Specific curing agents include 2,2',5,5'-tetramethylmethylenedi(cyclohexylamine). The tetraalkyl substitution pattern in a bridged cyclohexylamine derivative provides for extended pot life by retarding activity of the amine as a curative and the tetraalkyl substitution also enhances thermal properties of the epoxy resin.